1. Field of the Invention
The present invention relates to a testing apparatus for performing a setup testing or a hold testing on a device under test. More particularly, the present invention relates to a testing apparatus which is able to perform a setup testing or a hold testing efficiently. In addition, the present invention relates to the following Japanese patent application. The present invention claims the benefit of, and priority to, Japanese patent application No. 2002-289284 filed on Oct. 1, 2002, the entire contents of which are incorporated herein by reference for all purposes.
2. Description of Related Art
Recently, a requirement of high operation speed and low cost of an electronic device is prominent. According to the high operation speed, it becomes difficult to secure a setup time and a hold time of data transfer between electronic devices.
In case of writing data from the outside onto an electronic device using a clock as a reference, the data from the outside should be stabilized for more than a predtermined time before an edge of the clock in order to certainly write the data from the outside onto the electronic device. The predetermined time is referred to a setup time. Further, the data from the outside should be in a stable state until more than a predetermined time passes since an edge of the clock. The predetermined time is referred to a hold time. In case the conditions of the setup time and the hold time are not satisfied, sometimes the electronic device cannot perform holding of the data correctly.
Thus, it is required to test whether or not the electronic device secures the setup time and the hold time. The testing is performed by using a testing apparatus. Recently, the ratio of a cost for the test of the electronic device to a manufacturing cost of the electronic device becomes larger. Thus, in order to reduce the testing cost, reduction of time for the testing and improvement of accuracy of the testing are required.
A conventional testing apparatus measures a setup time which is necessary for writing data from the outside onto an electronic device by shifting gradually phase of the data from the outside with respect to a clock and judging whether or not it is possible to write correctly the data from the outside onto the electronic device. Further, a hold time is measured in a similar way. The data from the outside is provided to the electronic device according to a timing signal generated by the testing apparatus. Thus, it is required to generate a plurality of timing signals of which phase shifts gradually in order to measure the setup time and the hold time.
The testing apparatus stores a timing setting data showing a timing at which the timing signal should be generated to correspond to the data of the outside to be written and generates the timing signal according to the timing setting data. In other words, in order to measure the setup time and the hold time, it is required to store the timing setting data corresponding to each of the plurality of timing signals.
However, it is difficult to store all the timing setting data corresponding to all of the plurality of timing signals which should be generated. In order to store all the timing setting data, a memory of large volume is required. The conventional testing apparatus includes a register which is able to store several timing setting data. In case of generating the timing signal of which phase shifts gradually, it is required to rewrite sequentially the timing setting data stored in the register.
However, since it is required to stop a test pattern applied from the testing apparatus to the electronic device in order to write a new timing setting data on the resister, a dead time is generated in the testing of the electronic device. Thus, the time for the testing increases. Further, the manufacturing cost of the electronic device increase.
Accordingly, it is an object of the present invention to provide a testing apparatus and a testing method, which are capable of overcoming the above drawbacks accompanying the conventional art. The above object can be achieved by combinations described in the independent claims. The dependent claims define further advantageous and exemplary combinations of the present invention.